Generally, a display unit using a polarized light transducer polarizes light rays after receipt of them from an optical source, and converts the light rays into video signals before sending them to a screen. This device is classified as a reflecting type optical irradiating device, and a transmission type optical irradiating device.
First, the reflecting type optical irradiating device which is constructed, as shown in FIG. 1 operates in such a manner that light rays 11 incoming at a certain angle from an optical source 10 pass through a focussing lens 12 before passing through a transmission window 13a which is installed below a polarized light transducer 13.
Thereafter, the incident rays 11 are broken down into transmission light rays 11a passing through a polarizer 14 of the polarized light transducer 13, and reflected light rays 11b reflected from the polarizer 14. The reflected light rays 11b which are separated by the polarizer 14 pass through the transmission window 13b of the polarized light transducer 13, and are input into an optical/video converting device 15. Meanwhile, in accordance with the video signals which are supplied from a video signal generator 16, the optical/video converting device 15 changes the polarizing direction of the reflected light rays based on the brightness of the images. Then, the reflected light rays sequentially pass through a transmission window 13b, a polarizer 14 and a transmission window 13c of the polarized light transducer 13, and then, pass through an irradiating lens 18, before being sent to a screen 19.
Here, the light rays which are reflected from the optical/video converting device 15 are the ones which are subjected to a change of polarizing directions after the modification of the reflected light rays. Therefore, if they enter into the polarizer 14 again, the transmission component passes through it in accordance with the polarized direction, and the reflected component is reflected, thereby making it possible to distinguish the brightnesses. Meanwhile, the transmission type optical irradiating device which is constituted as shown in FIG. 2 operates in such a manner that incident light rays 11 which enter at a certain angle pass through a focussing lens 12, and then, pass through a transmission window 13a which is installed above a polarized light transducer 13. Thereafter, the incident light rays 11 are broken down into transmission light rays 11a passing through a polarizer 14 of the polarized light transducer 13, and reflected light rays 11b reflected from the polarizer 14. The reflected light rays 11b which are separated by the polarizer 14 pass through a transmission window 13b of the optical polarizing device 13, and then, are sent to a first color separating filter 20. Then of the three colors of R (red), G (green) and B (blue), the R color is reflected, and the remaining G and B colors are permitted to pass through a second color separating filter 21. Meanwhile, the R color which is reflected from the first color separating filter 20 is reflected again from a first reflecting mirror 22 which is disposed above the first color separating filter 20. Then, the R color reflected of the first color separating filter 20 passes through a liquid crystal panel 24 which is disposed at the front of the first reflecting mirror 22, and then sends to a first color synthesizing filter 23 which is disposed down stream thereof.
Of the G and B colors which have passed through the first color separating filter 20, the G color is reflected from the second color separating filter 21. Then the G color passes through a liquid crystal panel 25 which is disposed above the second color separating filter 20, and then, the G color is reflected from the first color synthesizing filter 23, before being synthesized with the R color. The B color which has passed through the second color separating filter 21 passes through a liquid crystal panel 26 which is disposed at the front of the second color separating filter 21. Then the B color is reflected from a second reflecting mirror 27 which is disposed at the front of the liquid crystal panel 27, and then, the B color is synthesized by a second color synthesizing filter 28. Then the R, G and B colors pass through a transmission lens 18, before forming an image on the screen 19. Under this condition, the liquid crystal panels 24, 25 and 26 are respectively provided with different transmissivities for the R, G and B colors, so that the colors on the screen should be decided in accordance with the supply of electrical signals. That is, if the R, G and B colors are applied to the liquid crystal panels 24, 25 and 26, a color image is regenerated on the screen.
However, in the above described optical irradiating apparatus for a display unit, much loss occurs in the light rays after they have passed through the polarizer after the emission of them from the optical source.
Because only the reflected light rays are used, the actual usable amount is about 50% of the total incident rays, thereby severely reducing the optical efficiency.